what is the building block of proteins?

Proteins are built from amino acids, which are the fundamental building blocks that link together to form polypeptide chains and ultimately functional proteins. Each amino acid has a common core structure around a central carbon (the α-carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) that gives each amino acid its unique properties. Proteins are formed when amino acids are joined by peptide bonds in a specific sequence dictated by genetic information, creating the protein’s primary structure. From there, the chain folds into higher-level structures (secondary, tertiary, and sometimes quaternary) driven by interactions among the side chains and the backbone, which determine the protein’s shape and function.